Simple methods of estimating source levels and locations of marine animal sounds.

This paper describes three relatively simple methods of estimating source levels of marine animal sounds by estimating the source distance acoustically, using one or two hydrophones. The methods are logistically simpler than using arrays of hydrophones of known positions but are accurate over a smaller range of distances. One method makes use of the differences in the arrival times and levels of the signals received at two hydrophones from the same sound emission. No knowledge of the positions of the hydrophones is required, however, if these are known the position of the source can be determined, with left-right ambiguity. The second method uses the difference in received levels only, but requires the hydrophone spacing to be known. Adequate accuracy requires the source to be significantly closer to one hydrophone than to the other. Third, if the direct and surface reflected arrivals can be separated, the source level can be determined with a single hydrophone. The methods require accurately calibrated hydrophones.